ISIS route summarization

In a level2 only ISIS network (not using multiple areas due to MPLS
limitations), is there a better method for handling aggregate routes
than creating an aggregate and redistributing it into ISIS for each
router? Primarily Cisco/Juniper based. Cisco I believe has an aggregate
option in ISIS (similar to OSPF) and Juniper has a separate aggregate
function which can be distributed into ISIS. Neither can do
summarization per say unless they cross between levels; unless I'm mistaken.
Offlist input is fine. Just trying to double check my brain while
setting up IPv6 on the access edges.
Link state does have it's limitations. ;)
-Jack